This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. The subproject and investigator (PI) may have received primary funding from another NIH source, and thus could be represented in other CRISP entries. The institution listed is for the Center, which is not necessarily the institution for the investigator. The Wildlife Toxicology Laboratory (PI Todd O'Hara) and Dr. Lora Ballweber (collaborator) from Colorado State University (molecular parasitolgy) propose a research topic in the area of gastrointestinal "ecology" of Hg distribution, dynamics and biotransformation in the intestine of select carnivores (piscivores) to determine relevance in bioavailability and potential toxicity. We will initially focus on macroparasites for which we will determine the "chemical feeding ecology" using C and N stable isotopes and the concentrations and proportions of total Hg and methyl mercury (MeHg). We then assess the compartments with the gut to determine if Hg is partitioning to specific compartments (including macroparasites). We will determine the "trophic level" of the parasite and determine if this correlates with THg and/or MeHg and compare the Hg concentrations within the parasite to the surrounding gut contents and that of other tissues (gut wall, liver, blood, etc.). Our first question asks;Does the "trophic level", morphometrics, location in the gastrointestinal tract, Se concentration, and genera/species of the macroparasite associate with whole parasite body Hg concentration as total Hg and MeHg as wet weight and dry weight? The second question is: Does the Hg concentration (total Hg and MeHg as wet weight and dry weight) of the gastrointestinal contents vary by location and/or fraction in the gastrointestinal tract and vary from that of the macroparasites (e.g., do the macroparasites biomagnify the Hg and/or biotransform it)?